Shoulder pain is a common musculoskeletal complaint among persons with disabilities and the general population, and can substantially impact their ability to perform functional activities. The majority of patients with shoulder pain have evidence of degenerative rotator cuff disease, yet simply identifying the rotator cuff as the source of pain proves insufficient to direct medical and rehabilitation strategies resulting in diminished treatment efficacy. Rehabilitation strategies typically focus on addressing abnormal shoulder motion believed to underlie the pain. However, the specific impact of abnormal scapular motion on the pathogenesis of rotator cuff disease is only theorized, thereby making it difficult for clinicians to target the most effective intervention strategies. The long-term objectves of my research are to identify movement-based mechanisms related to the pathogenesis of shoulder pain, and to develop and test the effectiveness of targeted rehabilitation interventions. will first assess the impact of decreased scapular upward rotation because it is a common clinically-observed movement dysfunction and is believed to cause rotator cuff compression, which can lead to rotator cuff disease. The specific aims of this proposal are to: 1) Determine the impact of decreased scapular upward rotation on rotator cuff compression in persons with shoulder pain; and 2) Identify the mechanisms by which sternoclavicular and acromioclavicular joint motion contribute to scapular upward rotation. My central hypothesis is that compared to asymptomatic controls, symptomatic individuals with decreased scapular upward rotation will have increased rotator cuff compression and will produce scapular upward rotation through different mechanisms. The proposed project will use advanced technologies and approaches for quantifying human motion and analyzing complex, multi-dimensional datasets. The research training plan has been developed specifically to accelerate the achievement of my long-term career objectives by strengthening scientific and professional skills, fostering networking and collaboration, and providing numerous opportunities to produce and disseminate research. The mentors for this proposal, Drs. Ludewig and Keefe, are well-suited to provide scientific and professional guidance as both are established researchers in the fields of biomechanics and multivariate data visualization and analysis, respectively. Both have a strong history of successful mentorship, publication, federal funding, and interdisciplinary collaborations. An advisory committee consisting of researchers and clinicians will provide content expertise in orthopaedic shoulder surgery, biomechanics, and statistics to help optimize the scope and impact of the proposed research. Receiving a Ruth L. Kirschstein NRSA Fellowship will enhance the synergy between my mentors, advisory committee, and the rich research environment at the University of Minnesota ensuring my future success as an independent and impactful researcher.